60 seconds (′′) = 1 minute (′)
60 minutes = 1 degree (°)
360 degrees = 1 circumference (cir.)
Circumference Degrees Minutes Seconds
1 = 360 = 21,600 = 1,296,000
A _quadrant_ is 1/4 of a circumference, or 90°; a _sextant_ is 1/6 of a
circumference, or 60°.
The length of a degree of longitude on the earth’s surface at the
Equator is 69.16 miles.
In astronomical calculation 30° are called a _sign_, and there are
therefore 12 signs in a circle.